SDL2 Demo in C

sdl2demo.c

#include <SDL2/SDL.h>
#include <stdio.h>

/* Screen dimension constants */
const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;

int error(char *msg, const char *err) {
  printf("Error %s: %s\n", msg, err);
  return 1;
}

int main(int argc, char *args[]) {
  (void)argc;
  (void)args;

  SDL_Window *window = NULL;
  SDL_Surface *surface = NULL;

  if (SDL_Init(SDL_INIT_VIDEO) < 0)
    return error("init", SDL_GetError());

  window = SDL_CreateWindow("A Really Cool Game", SDL_WINDOWPOS_UNDEFINED,
                            SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH,
                            SCREEN_HEIGHT, SDL_WINDOW_SHOWN);

  if (window == NULL)
    return error("window", SDL_GetError());

  Uint32 render_flags = SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC;
  SDL_Renderer *rend = SDL_CreateRenderer(window, -1, render_flags);
  SDL_RenderClear(rend);

  SDL_bool quit = SDL_FALSE;
  SDL_Event event;

  SDL_Rect rect;
  rect.x = 250;
  rect.y = 150;
  rect.w = 200;
  rect.h = 200;

  int right = 0;
  int left = 0;

  while (!quit) {
    while (SDL_PollEvent(&event)) {
      switch (event.type) {
      case SDL_QUIT:
        quit = SDL_TRUE;
        break;
      case SDL_KEYUP:
        switch (event.key.keysym.scancode) {
        case SDL_SCANCODE_D:
        case SDL_SCANCODE_RIGHT:
          right = 0;
          break;
        case SDL_SCANCODE_A:
        case SDL_SCANCODE_LEFT:
          left = 0;
          break;
        default:
          (void)0;
        }
        break;
      case SDL_KEYDOWN:
        switch (event.key.keysym.scancode) {
        case SDL_SCANCODE_D:
        case SDL_SCANCODE_RIGHT:
          right = 1;
          break;
        case SDL_SCANCODE_A:
        case SDL_SCANCODE_LEFT:
          left = 1;
          break;
        default:
          (void)0;
        }
        break;
      default:
        (void)0;
      }
    }

    if (right == 1) {
      rect.x += 1;
    }

    if (left == 1) {
      rect.x -= 1;
    }

    rect.x = rect.x % (SCREEN_WIDTH - rect.w);
    if (rect.x < 0)
      rect.x = SCREEN_WIDTH - rect.w;

    /* do stuff */

    SDL_RenderClear(rend);

    SDL_SetRenderDrawColor(rend, 255, 255, 255, 255);
    SDL_RenderFillRect(rend, &rect);
    SDL_RenderDrawRect(rend, &rect);
    SDL_SetRenderDrawColor(rend, 0, 0, 0, 255);

    SDL_RenderPresent(rend);

    SDL_Delay(1000 / 60);
  }

  /* close */
  SDL_FreeSurface(surface);
  surface = NULL;
  SDL_DestroyWindow(window);
  window = NULL;
  SDL_Quit();

  return 0;
}